Process for the preparation of polymerizable unsaturated compounds



Patented Dec. 7, 1937 Q UNITED STATES PATENT OFFICE PROCESS FOR THE' PREPARATION OF POLYMERIZABLE UNSATURATED COM- POUNDS No Drawing. Application December 5, 1933, Serial No. 701,053

10 Claims. (Cl. 260-106) This invention relates to a process for the preparation of unsaturated polymerizable organic compounds and more particularly to the preparation of such compounds from saturated organic compounds containing an isopropyl radical attached to a carbonyl group which likewise carries a hydrogen, hydroxy, aryl, or aralkyl group.

An object of the present invention is to provide an improved process for the preparation of polymerizable unsaturated aliphatic and/or aromatic organic compounds. Another object of the invention is to provide an improved process for the preparation of esters of the unsaturated monocarboxylic aliphatic organic acids. Another object of the invention is to provide an improved process for the preparation of methacrylic acid. A further object of the invention is to provide a process for the preparation of polymerizable esters of the unsaturated monocarboxylic aliphatic organic acids from aliphatic or aromatic organic compounds containing an isopropyl radical attached to a carbonyl group which likewise carries a hydrogen, a hydroxy, an alkyl, or an aryl group. A further object of the invention is to provide a process for the preparation of the methyl ester of methacrylic acid including the steps of catalytically dehydrogen-ating a compound containing an isobutyryl group and subsequently converting the thus obtained oxygenated compound to an alkyl ester of methacrylic acid. Other objects and advantages will hereinafter appear.

Valuable polymerizable unsaturated compounds are produced by dehydrogenation in accord with my invention and substantially as indicated by the equation:

2CH;CHCO=2CH'.-=CC0+H, Y i Y in which X may be an alkyl or aryl group and Y may be hydrogen, or a hydroxyl, alkoxy, aryl, alkyl, or aralkyl group. Thus by substituting an alkyl group such as methyl, ethyl, propyl or a higher group for X and hydrogen for Y,-' isobutyryl aldehyde, 2-methyl butyryl, aldehyde, and analogous aldehydes are indicated; these compounds being dehydrogenated to alphamethyl acrolein, alpha-ethyl acrolein, respectively, etc.; by the substitution of a hydroxyl group in lieu of hydrogen there would result Z-methyl propionic acid, Z-ethyl propionic acid, etc., which upon dehydrogenation would be converted respectively to methacrylic and ethylacrylic acids.

included under the term aryl include benzyl, naphthyl, and analogous aryl compounds. It will be appreciated by those skilled in this art that altho the substitutions in the X and Y positions will alter the reaction rates and in many instances the by-products resulting from the dehydrogenation, these substitutions are to be given but secondary consideration for, generally speak- .ing, if the compound to be dehydrogenated has the basic formula CH;(I}H l =0 and then esterified to the polymerizable methacrylate; from isobutyric acid, methacrylic acid which may be esterified to the ester; and in some instances from the alkyl esters of isobutyric acid the corresponding alkyl methacrylates are obtained directly. I usually prefer to convert the unsaturated compounds, if in the form of an aldehyde or acid, to the ester prior to polymerization.

Polymerization may be effected by any of the customary processes such, for example, as by heating, submitting the unsaturated compound to ultraviolet light, etc. Heat and/or light treatment may be augmented by the addition of peroxides, if desired.

The dehydrogenation of the above compounds I prefer, generally, to efiect in the vapor phase. Isobutyraldehyde, for example, is vaporized and passed at a. temperature within the range of 200-500 C., over a suitable dehydrogenation catalyst. The dehydrogenation may be conducted also. under elevated pressures, although usually I prefer to carry out the reaction under atmospheric pressure. A number of dehydrogenation catalysts may be employed for the treatment of isobutyryl containing compounds and theother compounds indicated above including, for example, nickel, copper, platinum, etc., the compound'catalysts such as copper-zinc-cadmium, copper chromite, and like well known catalysts.

I shall now describe several examples i1lus-.- trating my invention which, however, will be understood to limit in no way the operating conditions, equivalents, or scope thereof.

Example 1.Substantially anhydrous isobutyraldehyde was passed at atmospheric pressure and at a temperature of approximately 400 C. over 100 cc. charge of 8-14 mesh copper-chromiumzinc-cadmium catalyst at a space velocity of approximately 145. The catalyst may be prepared in accord with the patented process of Lazier, described in U. S. Patent No. 1,964,001. The exit gas issuing from the catalytic reaction was led thru a water condenser, and a cold trap cooled in a solid carbon dioxide-methanol bath. The exit gas was collected by displacement of water. A total condensate of 116 cc. was collected from the dehydrogenation of a 1.31. mols of isobutyraldehyde which contained an appreciable quantity of alpha-methyl acrolein, which is readily converted to the methyl ester of methacrylic acid by oxidation followed by esterification,well known oxidation and esterification processes may be used.

Example 2.After drying isobutyraldehyde over anhydrous calcium chloride and distilling, the thus dehydrated isobutyraldehyde, boiling between 63-64 0., was passed over a catalyst simi-- lar to that disclosed in Example 1 at a temperature of approximately 464 C., a space velocity of approximately 118, and at atmospheric pressure. 36 cc. of condensate was collected from the passage of .526 gram mol. of the oldehyde in a man- .ner similar to that disclosed in Example 1. The

condensate contained alpha-methyl acrolein, which on treatment in the liquid phase with potassium dichromate and dilute sulfuric acid may be converted to methyl acrylic acid, which in turn is esterified in the usual manner with an aliphatic alcohol to obtain an alkyl ester of methacrylic acid.

From a consideration of the above specification, it will be realized that any modification or improvement of the process herein described will come within the scope of my invention without sacrificing any of the advantages that may be derived therefrom.

I claim: a

1. In a processfor the preparation of polymerizable esters of methacrylic acid, the step which comprises dehydrogenating at reaction temperature isobutyraldehyde to alpha methyl acrolein in the presence of a dehydrogenating catalyst.

2. In a process for the preparation of polymerizable esters of methacrylic acid, the steps which comprise dehydrogenating isobutyralde-- hyde to alpha-methyl acrolein at a temperature of 200-500 C., and in the presence of a dehydrogenation catalyst adapted to the reaction. a

3. In a process for the preparation of polymerizable esters of methacrylic acid, the steps which comprise dehydrogenating isobutyraldehyde by passing it in the vapor phase over a copper-chromium-zinc-cadmium catalyst at a temperature of approximately 400 C.

4. A process of preparing an alkyl ester of methacrylic acid which comprises dehydrogenating isobutyraldehyde by passing it in the vapor phase over a dehydrogenation catalyst at a temperature between 200 and 500 0., and subsequently oxidizing and= esterifying the alphamethyl acrolein to an ester of methacrylic acid.

5. In a process for the preparation of polymerizable esters of methacrylic acid the step which comprises dehydrogenating isobutyraldehyde at a temperature of between 200 and 500 C. in the presence of a dehydrogenation catalyst.

6. A process of preparing a methyl ester of methacrylic acid which comprises dehydrogenating isobutyraldehyde by passing it in the vapor phase over a dehydrogenation catalyst at a temperature between 200 and 500 C., and subsequently oxidizing the product and esterifying the oxidation product with methanol.

'7. In a process for the preparation of polymerizable unsaturated organic compounds selected from the group consisting of alpha-aryl and alpha-alkyl substituted acrylic acid compounds the step which comprises dehydrogenating, in the presence of a dehydrogenation catalyst, a com pound in accord with the following equation:

in which X is a radical selected from the group consisting of alkyl and aryl radicals.

8. In a process for the preparation of polymerizable unsaturated organic compounds selected from the group consisting of alpha-aryl and alpha-alkyl substituted acrylic acid compounds, the step which comprises reacting a compound having the basic formula:

in which X is a radical selected from the group consisting of alkyl radicals and aryl radicals, in the presence of a dehydrogenating catalyst.

9. In a process for the preparation of an alkyl ester of methacrylic acid, the steps which comprise dehydrogenating a compound selected from the group consisting of isobutyraldehyde, isobutyric acid, and its esters by passing the compound in the vapor phase over a dehydrogenation catalyst at a temperature between 200 and 500 C.

10. In a process for the preparation of polymerizable esters of methacrylic acid, the steps which comprise dehydrogenating a compound selected from the group consisting of isobutyraldehyde, isobutyric acid and its esters by passing the compound in the vapor phase over a copperchromium-zinc-cadmium catalyst at a temperature of approximately 400 C.

JOHN C. WOODHOUSE. 

